In recent years, optoelectronics have garnered attention as a key technology for realizing, for example, higher-speed information communications or various smaller and lighter electronic devices, and the development of optical materials for achieving these has become imperative.
Conventionally, inorganic materials such as optical glass commonly have been used as optical materials. However, inorganic optical materials are difficult to process, and they have the inherent problem of difficulty to produce optical components, which increasingly have become finer and more complex, in a large quantity and at low cost, by using inorganic optical materials.
On the other hand, organic optical materials typified by resins have excellent workability, can be produced at a reduced cost, and moreover, they are lightweight. Therefore, organic optical materials are expected to serve as the materials for supporting future optoelectronics technology, and their development tends to accelerate in recent years.
The problems of organic optical materials include that an optical component formed of an organic optical material alone does not provide a sufficiently high refractive index, and that there are few organic optical materials that are well-balanced in terms of the refractive index and the dispersion. It is known that the refractive index nmD at the D-line (wavelength: 589 nm) of resin materials, which are most commonly used as the organic optical material, and their Abbe's number νm, which indicates the dispersion, largely satisfy Formula (1) below (see Non-patent Document 1). It should be noted that since the wavelength of the D-line and that of the d-line (wavelength 587: nm) are very near, the refractive index at the D-line and that at the d-line of each of the materials can be considered to show substantially the same tendency.1.66−0.004 νm≦nmD≦1.8−0.005 νm  (1)
For example, in the case where a lens serves as the optical component, the fact that the refractive index of the resin is not sufficiently high and the fact that there are few materials that are well-balanced in terms of the refractive index and the dispersion lead to the problem that sufficient characteristics cannot be achieved owing to chromatic aberration or field curvature. Furthermore, in the case where a solid-state image sensor including an optical waveguide serves as the optical component, a sufficient refractive index difference between the optical waveguide and the surrounding materials cannot be achieved, which results in the problem of a reduced light collection efficiency.
In order to solve these problems, studies have been made to disperse inorganic fine particles in a resin serving as the substrate to prepare an organic optical material with a high refractive index, and to use this material to form an optical component. Patent Document 1 discloses a method for forming an optical component from a resin composition in which fine particles of alumina, yttrium oxide or the like are dispersed in a transparent substrate resin such as a methacrylic resin as a method for obtaining an optical component made of an organic optical material exhibiting a high refractive index and low dispersion. Patent Documents 2 to 4 disclose methods for forming an optical component from a thermoplastic resin composition in which fine particles of titanium oxide or zinc oxide are dispersed in a thermoplastic resin having a certain level of optical characteristics.    Patent document 1: JP2001-183501 A    Patent document 2: JP2003-073559 A    Patent document 3: JP2003-073563 A    Patent document 4: JP2003-073564 ANon-patent document 1: “Kikan Kagaku Sosetsu (Quarterly Chemical Review) No. 39 Control of refractive index of transparent polymer”, Fumio Ide, edited by The Chemical Society of Japan, issued on Nov. 10, 1998, page 9, FIG. 2)